Kevin Johnson, Microsoft's online and Windows chief and a key figure in the company's failed Yahoo takeover effort, is leaving the company to become chief executive at Juniper Networks, Microsoft confirmed on Wednesday in the US.

Kevin Johnson
(Credit: Microsoft)

No immediate successor has been named for Johnson (pictured), who, as president of Microsoft's Platforms & Services Division, had reported directly to chief executive Steve Ballmer.

In conjunction with Johnson's departure, Microsoft plans to split its Windows and online-services division into two separate units, as they had been up until a couple of years ago. Microsoft is searching both inside and outside the company for a new online-services chief, the company stated.

The company did not say how it plans to handle Windows duties, other than that Bill Veghte, senior vice president of the Online Services & Windows Business Group, and Steve Sinofsky, who runs engineering operations, would report to Ballmer. Microsoft said Johnson's other immediate direct reports will also now report directly to Ballmer.

Juniper Networks did not immediately respond to requests for comment.

In a statement announcing Johnson's departure, Ballmer praised Johnson's contribution to the company.

"Kevin has built a supremely talented organisation and laid the foundation for the future success of Windows and our online-services business. This new structure will give us more agility and focus in two very competitive arenas," Ballmer said. "It has been a pleasure to work with Kevin, and we wish him well in the future."

As chief of Windows and Windows Live, Johnson was spearheading Microsoft's revamped online search and advertising strategy, which is considered key if Microsoft is to catch Google in the online search arena. Johnson outlined the new strategy in a memo to his team in May, while Microsoft was actively pursuing Yahoo. The takeover of Yahoo was expected to be a big boost to that effort.

After the first round of Microsoft's as-yet failed bid for Yahoo, Johnson, in a memo, tried to downplay the failure, saying that part of the reason Microsoft abandoned its offer to buy Yahoo was that speed was paramount in the purchase.

Last month, Johnson added to the Microsoft-Yahoo drama when the Financial Times Deutschland reported that he said the software giant would be interested in bidding on a Yahoo under new management. However, according to a Microsoft representative, Johnson did not suggest such a scenario.

Johnson, who joined Microsoft in 1992, was named co-president of the Windows and online division as part of a sweeping reorganisation of the company in 2005. When Jim Allchin, the other co-president, retired a year later, Johnson assumed sole control.

Johnson was appointed group vice president of Microsoft's worldwide sales, marketing and services in 2003 after success leading the North and Latin America sales team. Before joining Microsoft, Johnson worked in the systems integration and consulting business unit at IBM, and as a software developer in the petroleum and financial-services industries.

CNET News.com's Steven Musil contributed to this report.